Flat film plastic extrusion apparatus

ABSTRACT

A die assembly for multiple layer extrusion onto a paper web substrate is movable on an overhead support beam from an on-line position over a laminating station to an off-line position transversely adjacent such station. A pair of stationary extruders feed plastic material to the die assembly through a pair of movable feed assemblies each of which includes two straight sections of conduit connected to each other by a rotary joint and connected to the extruder and to the die assembly by further rotary joints so that movement of the die assembly is enabled by a swinging and folding movement of the conduit sections. An improved die adapter is also disclosed for the simultaneous three-layer co-extrusion from the two extruders in which the film thicknesses of the outer layers are controlled with respect to the center layer.

@S atent [191 [111 3,734,662 armon et al. [451 May 22, 1973 [541 FLATFILM PLASTIC EXTRUSION 3,299,474 1/1967 Ashworth ..425 190 x APPARATUS3,559,239 2/1971 Work et al ..425/131 [75] Inventors: Paul E. Harmon,Fulton; Kenneth A. Primary Examiner j Spencer Overholser Mamstone oswegaboth of Assistant ExaminerMichael 0. Sutton 13069 Attorney-Marechal,Biebel, French & Bugg [73] Assignee: The Black Clawson Company,

Hamilton, 01110 [57] ABSTRACT [22] Filed; 3, 7 A die assembly formultiple layer extrusion onto a paper web substrate 1s movable on anoverhead sup- PP N04 113,310 port beam from an on-line position over alaminating station to an off-line position transversely adjacent [52] US. Cl 425/131 425/190 425/376 such station. A pair of stationaryextruders feed plastic 425/462 material to the die assembly through apair of movable 51 1m. 01. .3291 3/00, B29f 3/04 assemblies f whichincludes Straight [58] Field of Search 425/131 132 182 sect1ons ofcondult connected to each other by a ro- 188 6 tary joint and connectedto the extruder and to the die assembly by further rotary joints so thatmovement of the die assembly is enabled by a swinging and folding [56]References cued movement of the conduit sections. An improved die UNITEDSTATES PATENTS adapter is also disclosed for the simultaneousthreelayerco-extruslon from the two extruders 1n wh1ch the 2,816,741 12/1957Shuffman ..259/8 film thicknesses of the outer layers are controlledwith Corbett respect to tha center layer 2,197,988 4/1940 Tanzi..425/19O X 2,518,744 8/1950 Bamhard ..l56/37l 4 Claims, 10 DrawingFigures PATENTEW 3.734.662

SHEET 1 BF 3 IN VE IV TORS PAUL E. HARMON 8 KENNETH H. MAINSTONE ATTOR/VEYS SHEET 3 OF 3 PEG-8 FLAT FILM PLASTIC EXTRUSION APPARATUSBACKGROUND OF THE INVENTION In single or multi-layer extrusion ofplastic sheet material or the like, commonly one or more extruders areconnected to a die positioned at a forming station. Generally suchextruders are connected directly to the die or by a rigid conduit whichextends over the forming station, and the extruder is supported on amovable dolly or tracks so it may be moved to an online position.

One problem with this arrangement is that it handicaps the efficiency ofstart-up operations which are performed at a location spaced from theforming station. Generally the extrusion is begun at such location andthe die is adjusted, and then, while extrusion is taking place, theentire extruder-conduit-die assembly is moved and locked into operatingposition.

Tracks and mechanical moving means also present certain problems. Thetracks must be long enough to permit the extruder to retract asubstantial distance to place the die in a position for cleaning oradjustment. This unnecessarily wastes valuable plant spaceandcorrespondingly increases the cost of the installation. In addition, aperiod of time isrequired to adjust the particular die in both thelongitudinal and lateral directions with respect to the formingstationcenterline, as well as in gauge thickness and-width of extrusion andsuch adjusting procedure is often a.hit-or-miss operation.

In multi-layer extrusion where more than one extruder is utilized, theproblems referred to above are essentially multiplied. For example,where two extruders deliver different plastic materials to thedie,either one extruder obstructs the path of the other or'it must belocated in opposed relation to it, and consequently the maneuverabilityand spaceproblems arecorrespondingly increased.

SUMMARY OF THE INVENTION- The present invention is directed to a novelextrusion feed assembly which enables extruded material to be conveyedfrom one or more stationary extruders to a forming station withsubstantially increased efficiency and maneuverability. The feedassembly facilitates start-up and maintenance, andv has substantiallyincreased flexibility as compared with prior practice. An improved dieadapter is also disclosed for the coextrusion of two polymers from twoextruders in a flat film die.

Generally, the feed assembly comprises a movable conduit assembly formedof two or more conduit sections converted by rotary joints between the:extruding station and the forming station. The dieand die adapter aresupported on a beam for movement from a retracted off-line positionadjacent the stationary extruders to an extended on-line position abovethe forming station. A reversible traverse motor is mounted on thesupport beam for moving the die between the extended lel and are normalto the direction of movement of the die on the support beam so thetransverse movement of the die is accompanied by a simple pivotalmovement of the conduit sections.

Multi-layer lamination sheets are formed by conveying the output fromtwo or more extruders through corresponding movable or flexible conduitassemblies to an adapter mounted on the die. A three-layer sheet isformed by passing the output from one extruder through a central passagein the adapter and the output from another extruder through a secondpassage having branch inlet passages. A pair of inclined passagescommunicate with the branch passages and converge with the centralpassage at the outlet of the adapter where the several layers arecombined for delivery to the die inlet. A pair of choker bars havingbeveled faces adjust the cross-sections of the branch passages and,together with the extruder output pressures, vary the relativethicknesses of the individual layers in the sheets.

BRIEF DESCRIPTION OF THE DRAWING FIG. l is a side elevation of theextrusion feed assembly of the present invention disposed between aforming station and an extrusion station;

FIG. 2 is-a top view of the extrusion feed assembly of FIG. 1;

FIG. 3 is a partially broken-away end view of the extrusion feedassembly of FIG. 1;

FIG. 4 is a fragmentary sectional view taken generally along line 4-4 ofFIG. 2 and showing one of the rotary conduit assemblies;

FIG. 5 is a sectional view taken generally along the line 5-5 in FIG. 4"and showing a representative connection between a rotary connector and atubular arm;

FIG. 6'is a side view of the adapter with one of the side plates removedlooking generally along line 66 in FIG. 8;

FIG. 7 is a fragmentary side view of the adapter adjusting mechanism;

FIG. 8 is a partially broken away end view of the adapter;

FIG. 9 is a transverse section along line 9-9 of FIG. 8; and

FIG. 10 is a transverse section along line l010 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1-3, anextrusion feed assembly constructed according to the invention extendsbetween a forming station indicated generally at 11 and a transverselyspaced extruding station indicated generally at 12. The details of theforming station, as such, form no part of the present invention and isshown as comprising a laminator in which an extended sheet or film ofplastic material is applied to one side of a web of paper. lt'is withinthe scope of the present invention to provide for extrusion of a singleor multiple layers of plastic material without lamination. As shown inFIGS. 1 and 3, a chill roll 13 is supported on a transverse shaft 14. Aweb 15 of paper is delivered over a guide roll 16 to a nip formed by asmall pressure roll 17 and a back up roll 18. The plastic material isapplied to the web 15 at a point above the pressure nip and is carriedby the web through the nip and against the chill roll 13. The combinedlaminated paper and plastic film web is removed from the chill roll 13by a stripper roll 19.

The apparatus of the present invention is adapted for the application ofeither single or multiple film extrusion, and for the purpose of thepreferred embodiment, a multiple layer co-extrusion assembly isillustrated generally at 20 and includes a flat film die 21 and a dieadapter 22 mounted at the die inlet for feeding the polymer from two ormore extruders to the die 21. The extrusion die 21 used with the presentinvention may be as shown and described in the patent of Hoffman et al.US. Pat. No. 3,142,090 assigned to the same assignee as this invention,with a single central inlet and an internal spreader or coat hangerdrape" passage leading from the inlet to the elongated extrudingorifice. Band or induction heaters maintain the die at extrudingtemperature.

Means for supporting the die assembly 20 for transverse movement from anon-line position as shown in full lines in FIG. 1 to an off-lineposition as shown in broken lines in FIG. 1 includes a cross beam 24comprising an overhead support track. The cross beam 24 is supported onrails 24 and slidably receives a movable support member 25. Traversingmovement of the support member 25 with respect to the beam 24 isprovided by a drive motor 26 through a conventional lead screw driveapparatus. The die 21 is shown as being mounted in suspended relation onthe member 25 by means of a pair of vertical support beams 27. By thismeans, the die 21 can be moved from the off-line position to the on-lineposition as shown in FIG. 1.

A first stationary screw type extruder 30 is positioned along an axisline 31 along one side of the forming station 11, while a secondstationary screw type extruder 32 is disposed generally along the sameaxis line in facing relation to the extruder 30. The extruders 30 and 32respectively deliver molten polymer under elevated temperatures andpressure through the usual control valve and screen pack devices mountedon the ends of the extruder barrel and illustrated generally at 34. Theextruders may be of the same capacity or may be of different capacitiesin accordance with the delivery rate and thicknesses desired for theindividual laminates.

The invention further provides a novel flexible or movable conduitassembly for connecting each of the extruders 30 and 32 for feedingplastic material to the die assembly 20. To this end, separate andessentially identical conduit assemblies 40 are provided for each of theextruders. 1

Thus, the conduit assemblies 40 include a first conduit section 41 andhas one end connected to receive plastic material through a first rotaryjoint 42. A second rotary joint 43 connects the first conduit section 41to a second conduit section 44. The remote end of the second section '44is connected to apply plastic material to the die adapter 22 through athird rotary joint 45. In installations where only a single film orthickness of plastic film material is to be extruded only one extruderand one assembly 40 would be used and the conduit section 44 and rotaryjoint 45 would be connected to apply molten plastic material directly tothe die inlet.

The joints 42, 44 and 45 (FIG. 4) are all of similar construction andinclude central cylindrical body portions 46 formed with threaded ends46' of reduced diameter and spaced flanged inner ends 47 of greaterdiameter. All have L-shaped passages 48 which pass through the flangedand central portions and open into outlets 49 in the outer surfaces ofthe central portions 46. The outlets 49 are flared in the radialdirection (FIG. for rotary communication with the passages in thetubular conduits.

Each joint has a tubular or sleeve-like graphite bushing 50 receivedover the associated central portion 46 between a pair of hightemperature seals 51, and has a slot 52 aligned with the outlet 49. Atubular rotatable sleeve 54 is received around each graphite bushing 50and is retained around the central portions 46 by a retainer nut 55received on the threaded ends 46 of the joints, and by lock nuts 56tightened thereagainst. The

tubular sleeves 54 have a flat surface 57 cut along a chord therein, andhave recesses 58 with uniformly flared openings 59 which communicatewith the slots 52 in the bushings 50. The ends of the conduit sections41 and 44 are received in the recesses 68 and attached to the sleeve 54by a rectangular flange 60 which is welded to each end of the conduitsand mates against the flat surfaces 57. Suitable bolts secure theflanges to the rotatable sleeves through appropriate holes in each sideof the flange.

The intermediate joint 43 is adapted to pivot on an arc (FIG. 1) aboutthe discharge end of the extruder and to rotate the conduit arms throughthe rotary sleeves 54 and accordingly includes, in addition to theaforementioned features, a recess 61 in one side of the flanged end 47for rigidly receiving one end of the conduit 41. An S-shaped passage 62connects the passages in each of the conduits 41 and 44 and is closed bya plug 63 with a beveled end inserted into the flanged end of theS-shaped passage 62.

To maintain the fluid state of the plastic material as it is conveyedthrough the conduit assemblies 40, band heaters 65 are secured aroundthe central portions 46 of each joint 42, 43 and 44, and around theflanged end 47 of the intermediate joint 43. Circular heaters 66 arewrapped around the conduit sections 41 and 44. The interconnected andflared passages within the rotary connectors permit the fluid plastic toflow through the die as it is moved between its on-line or extendedposition to its off-line or retracted position. The axes of rotation ofeach of the joints is parallel to that of the extruder and normal to themovement of the die 21 on the overhead beam 24. This arrangementadvantageously provides an overall compact assembly.

In the preferred embodiment of the invention, the extruders 30 and 32deliver two plastic materials of differing characteristics to the dieadapter 22 respectively through L-shaped connector conduits 67 and 68which are connected at one end to the adapter inputs and which havetheir other ends connected respectively to one of the rotary joints 45.The adapter, itself, is designed to split the flow of polymer from oneof the extruders into two streams and the flow of the other of theextruders into a single stream and to join these streams internally toform three separate and distinct layers of material. The material thusjoined is applied to the inlet of the die 21.

Referring to FIGS. 6-10, the adapter 22 is shown as including a centraland generally rectangular body 70. The body 70 is flanked on two of itsopposite sides by a pair of essentially identical side blocks 71 and 72,and is further flanked on the remaining two opposite sides by flangedend plates 73 and 74. The end plates, together with the side blocks,define internal passageways within the adapter. The end plate 73, asshown in FIG. 9, defines a first polymer inlet 75 leading to an internalbranching passageway 76. As seen, the passageway 76 is formed half inthe body and half in the end plate 73 for convenience of manufacture.The passageway 76 leads to a pair of parallel branches 77 and 78. Thesebranches are, again, formed partially in the body 70 and partially inthe respective side blocks 71 and 72.

The branches 77 and 78 communicate with converging slot-like passageways80 again defined between the center body 70 and the side blocks 71 and72, as best shown in FIG. 6. These passages converge at the bottom ofthe body 70 above a rectangular adapter outlet 82.

A second adapter inlet 84 is defined in the end plate 74 and leadsdirectly into a central passageway 85 formed in the body 70. The bottomportion of the central passageway 85 opens into a constricted channel86, again best shown in FIG. 6. The constricted upper portion 86 of thepassageway 86 is designed for the purpose of regulating the rate of flowfrom the associated extruder into the die outlet. The bottom of passage86 also opens centrally into the outlet 82 midway between the regions atwhich the converging passages 80 open into this outlet. Accordingly,flow from the extruders into the inlets 75 and 84 form a three-layerlaminate at the outlet 82.

The ends of the passages 77, 78 and 85 opposite to that of the inletsare closed by identical closure plugs 88. One such plug is shown inelevation in FIG. 8. The closure plug has a cylindrical body portion 89and an arcuately curved end 90 which defines a transitional flow controlsurface. The plug is keyed in predetermined alignment by a pin 92.

Means for regulating the rate of flow through the respective passages 80includes a pair of choker bars 94 which have tapered ends 95 receivedand effectively forming a portion of one side wall of the channels 80.Adjustable bolt assemblies 96 have lower ends which connect with thechoker bars 94 through openings 96 formed in the side plates 71 and 72.The bolts 97 are axially adjustable through a packing nut 98 and packing99 by an adjusting mechanism 100 mounted on a U-shaped plate 102, asbest shown in FIG. 7. The plate 102 haslegs 103 which are bolted to theend plates 73 and 74 through openings 105, and have central connectingsections which support a threaded collar 112. A threaded operator sleeve114 has external threads in the collar 112 and internal threads receivedover a threaded end of the bolt 97 to effect accurate adjustment of theportion of the choker bar 94 within the associated channel 80. Thechoker bars 94 are operated in conjunction with the variablespeedextruders to regulate the thickness of each lamination layers. Theoverall thickness of the layer is, of course, defined by the dimensionsof the outlet 82 and this will determine the relative thickness of eachlayer of the resulting film.

The die adapter 22 is maintained at an elevated temperature by suitableheating means which may comprise electric resistance heaters 115 mountedon the top and 116 mounted on the sides as shown in FIG. 6. Thermocouple1 18 may extend into the body 70 for the purpose of monitoring thetemperature. Flanges 120 are formed on the bottoms of the end plates forattachment to the die 21.

From the drawing and above description, it is apparent that a feedassembly in accordance with the invention provides desirable featuresand advantages. The assembly enables extruders to be fixed at one placeon the floor and the die may be retracted to a position spaced from theforming station for start-up or maintenance purposes without moving theextruders. This feature enables the extrusion operation to be started atthe retracted position, where the relative thicknesses of the layers maybe adjusted, and the die may thereafter be advanced to its on-lineforming position, thereby facilitating start-up and substantiallyincreasing the efficiency of the forming operation.

Since the rotary feed assemblies eliminate the need for movableextruders, which are heavy and difficult to maneuver, a larger selectionof extruder sizes may be employed. In addition, the spacing of theextruders from the forming section can be altered to suit particularapplications simply by varying the lengths of the tubular conduitsections, and this feature, together with the rotating connectors,eliminates the need for constructing special conduits for eachoperation. Inclusion of the combining adapter in the feed assembly alsoeliminates the need for special external valving from the extruders tothe die, and simplifies multi-layer sheet extrusions by providing ameans for delivering the extruded outputs to a single die inlet. Therotary conduit assembly allows at least two extruders to be used simultaneously without doubling the problems incident to movable extruders,and the extruders may be spaced from an parallel to the centerline ofthe forming station to conserve valuable plant space.

While the structures 30 and 32 are shown as being positioned on a commonaxis 31, it is obvious that the extruders may be positioned in laterallyoff-set relation or on separate axes, and the lengths of the arms 41 or44 varied as necessary. Further, it is within the scope of the inventionto move the extrusion assembly 20 vertically with respect to the roll13, the vertical movement being accompanied by corresponding pivotalmovement at the joints 45, 43 and 42. For example, vertical movement ofeither end of the extrusion die may be accomplished at the supports 27,and these supports may comprise adjusting cylinders or includescrew-type adjustments. Further, the die assembly may be raised orlowered vertically, as a unit, either by a suitable adjustment at thesupports 27 or by a lifting mechanism carried within the support member25.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. An extrusion feed assembly adapted to convey fluid plastic materialfrom at least two stationary extruders to a die for extruding saidmaterial in a multilayer sheet form at an extrusion station, comprisingsupport means disposed above said extrusion station and said extruders,an adapter attached to said die, means mounting said die and adapter onsaid support means for movement between an advanced on-line positionabove said extrusion station and a retracted offline position spaced atone side of said station, and separate rigid conduit means eachincluding intermediate rotary means connecting each extruder to saidadapter for delivering said material to said die as it is moved betweensaid on-line and off-line positions.

2. An extrusion feed assembly as defined in claim 1 wherein each saidconduit means includes first and second conduit sections, anintermediate rotary connector disposed between and joining said sectionsfor pivotal movement, first joint means forming a rotary connectionbetween one said extruder and said first conduit section, and secondjoint means forming a rotary connection between said second conduitsection and said die, said rotary connections having planes of rotationnormal to the direction of movement of said die support means.

3. A multiple film extruder assembly comprising an extruder station, afirst screw-type extruder at one side of said station for extruding afirst polymer, a second screw-type extruder positioned adjacent saidstation at said one side thereof for extruding a second polymer, diemeans having a pair of inlets and adapted to apply said polymers in amulti-layer sheet, elongated support means disposed above said stationand extending transversely to a position adjacent said station at saidone side thereof, means mounting said die means on said support meansfor movement between an on-line position above said station and anoff-line position at said one station side, and separate rigid, movableconduit means connecting said extruders to said die means inlets whileproviding for said die movement 4. The assembly of claim 3 in which saidconduit means each have a pair of pivotally interconnected rigid conduitsections including means defining a first rotary connection between oneof said sections and said die means and a second rotary connectionbetween the other of said sections and one of said extruders.

1. An extrusion feed assembly adapted to convey fluid plastic materialfrom at least two stationary extruders to a die for extruding saidmaterial in a multi-layer sheet form at an extrusion station, comprisingsupport means disposed above said extrusion station and said extruders,an adapter attached to said die, means mounting said die and adapter onsaid support means for movement between an advanced on-line positionabove said extrusion station and a retracted off-line position spaced atone side of said station, and separate rigid conduit means eachincluding intermediate rotary means connecting each extruder to saidadapter for delivering said material to said die as it is moved betweensaid on-line and off-line positions.
 2. An extrusion feed assembly asdefined in claim 1 wherein each said conduit means includes first andsecond conduit sections, an intermediate rotary connector disposedbetween and joining said sections for pivotal movement, first jointmeans forming a rotary connection between one said extruder and saidfirst conduit section, and second joint means forming a rotaryconnection between said second conduit section and said die, said rotaryconnections having planes of rotation normal to the direction ofmovement of said die support means.
 3. A multiple film extruder assemblycomprising an extruder station, a first screw-type extruder at one sideof said station for extruding a first polymer, a second screw-typeextruder positioned adjacent said station at said one side thereof forextruding a second polymer, die means having a pair of inlets andadapted to apply said polymers in a multi-layer sheet, elongated supportmeans disposed above said station and extending transversely to aposition adjacent said station at said one side thereof, means mountingsaid die means on said support means for movement between an on-lineposition above said station and an off-line position at said one stationside, and separate rigid, movable conduit means connecting saidextruders to said die means inlets while providing for said diemovement.
 4. The assembly of claim 3 in which said conduit means eachhave a pair of pivotally interconnected rigid conduit sections includingmeans defining a first rotary connection between one of said sectionsand said die means and a second rotary connection between the other ofsaid sections and one of said extruders.